Liquid fuel burner



Dec. 1, 1964 W. C. SCHULING ETAL LIQUID FUEL BURNER Filed Jan. 30, 1962INVENTORS WlLH-ELMUS c. SCHULINQG HENRI VERKOREN HENDRIK J. KOS'YI'ERTHEIR ATTORNEY United States Patent 3,159,200 LIQUID FUEL BURNERWilhelrnus C. Schuling and Henri Veriroren, Amsterdam,

and Hendrik J. Koster, Rotterdam, Netherlands, assignors to Shell OilCompany, New York, N .Y., a corporation of Delaware Filed Jan. 30, 1962,Ser. No. 169,787 Claims priority, application Belgium, Feb. 13, 1961,477,481, Patent 600,137 1 Claim. (Cl. 158-1) The invention relates to acombustor for liquid and/ or gaseous fuels to be applied, for example,in a boiler or in an industrial furnace to heat liquids like petroleumor petroleum fractions.

In accordance with a widely used construction such combustors consist ofa burner placed centrally in an opening in the wall of the combustionspace, so that concentrically around the burner an annular space isprovided for admission of the combustion air.

The opening in the wall of the combustion space is in its simplest formcylindrical, delimited by the two sides of the furnace front and acylindrical cavity in the brick wall. In this case, the burner is placedin the axis of the cylinder. A cone-shaped cavity in the brick wall isanother possibility. Such constructions have been described, forexample, in British Patent 447,624 and in French Patent 961,605.

It has now appeared that shape and dimensions of the cavity in questionare of fundamental importance for the combustion pattern and especiallyfor the shape and the stability of the flame. In the constructions asapplied up to now, at certain loads a strong spreading of the flameinvariably occurred, Which caused this flame to touch the furnace frontand also the tubes built in the front. This had an adverse effect on thelife of the furnace wall, while also local overheating of the tubessituated near the furnace front sometimes caused serious difiiculties.

It was now found that these problems do not occur when the burner isplaced in a bowl-shaped recess of special dimensions. The inventiontherefore relates to a combustion device for liquid and/ or gaseousfuels, consisting of a burner placed centrally in a bowl-shaped recessin the wall of a combustion space, an annular opening for the combustionair being provided coaxially between the burner and the edge of therecess, the shape of the recess being such that the following conditionsare satisfied:

(a) The ratio between the smallest diameter and the largest diameter ofthe recess (d/D) is between 0.58 and 0.72.

(b) The ratio of the length to the largest diameter of the recess (l/D)is between 0.45 and 0.55.

(c) The angle (alpha) formed by the wall of the bowlshaped recess andthe surrounding wall of the combustion space where it enters thecombustion space is between 95 and 100.

By applying this construction the shape of the flame can be completelycontrolled and, particularly, the flame can be prevented from spreading.The flame obtained with this construction is slender and compact, sothat contact between the flame and the furnace front and front tubes isprevented, and longer life of the materials is obtained.

The recess should be bowl-shaped, the concave side be- 3,159,200Patented Dec. 1, 1964 ing turned towards the combustion space. Thegenerating line of the recess is preferably in the form of an arc of acircle, the ratio between the radius of this are and the largestdiameter of the recess (r/D) being between 0.70 and 1.50. The generatingline can also have another shape, for example, that of a parabola.

If the burner is used for burning liquid fuel like residual fuel oil, itis provided with an atomizer for the fuel. Conventional pressure jetburners are particularly suitable, but steam jet burners may also beemployed.

Burners suitable for burning both liquid and gaseous fuels can also beused. A suitable construction for this type of burner is described inBritish Patent 755,389.

The air necessary for combustion enters the combustion space via anannulus between the burner and the wall of the recess. To control theamount of combustion air, an air register fitted on the outside againstthe furnace front is generally used. A very suitable construction for anair register to be used for the construction according to the inventionis described in U.S. Patent 2,515,843. In this construction part of thecombustion air is caused to rotate by means of a plurality of annularlyplaced blades and led into the combustion space via the circumference ofthe recess,'while another part of the air, caused to rotate in theopposite direction by another set of blades, is directed into thecombustion space immediately around the burner.

The construction according to the invention will now be described inmore detail with reference to the accompanying drawing.

In this drawing, 1 represents the wall of the combustion space, such asthe furnace of a steam boiler or of an industrial furnace, for heatingfor example petroleum or petroleum fractions. This wall has abowl-shaped recess 2 which, because of the excessive thermal load, ispreferably made of a heat-resistant material 3 like sillimanite.

In the bowl-shaped recess, a burner 4 for liquid or gaseous fuel isfitted concentrically. If the combustor is used for burning liquidfuels, like residual oils or bitumen, this burner is provided with anatomizer 5, for example, a pressure jet atomizer of known construction.

The air necessary for the combustion is fed via air register 6, also ofknown construction. The air entering at 6 is preferably brought torotation by means of a plurality of blades, which promotes the mixing ofthe air and the fuel and thereby also the stability of the flame formedin the recess. Usually part of the combustion air is fed to thecombustion space via the inlets 7 which are annularly placed aroundburner 4, rotating in a direction opposite to that of the air enteringat 6.

The shape of the recess is determined by the largest diameter D at theentrance into the combustion space, the smallest diameter d, the lengthl and the angle alpha formed by the wall of the recess at the entranceinto the combustion space and the surrounding wall of this combustionspace.

For the construction given in the figure:

(a) The ratio d/D=0.65 (b) The ratio l/D=0.48 (c) The angle alpha=97 (d)The ratio r/D=1.00

We claim as our invention: A combustion device for liquid and/or gaseousfuels, comprising a burner placed centrally and rearwardly in a recessin the wall of a combustion space, an annular opening for the combustionair being provided in the wall of the combustion space coaxially betweenthe burner and the edge of the recess, characterized in that the recessis bowlshaped and that the largest diameter thereof opens into thecombustion space and the smallest diameter thereof is remote from saidspace, the following conditions being satisfied:

(a) the ratio between the smallest diameterand the largest diameter ofthe recess (d/ D) is between 0.58 and 0.72;

(b) the ratio of the length between the two said diameters to thelargest diameter of the recess (ND) is between ;45 and 0.55;

(c) the angle (alpha) formed by the wall of the bowlshaped recess andthe surrounding Wall of the combustion space at the entrance to thecombustion space is between and and (d) the generating line of thebowl-shaped recess is the arc of a circle, the ratio of the radius ofthis are to the largest diameter of the recess (r/D) being between 0.70and 1.50.

References Cited in the file of this patent UNITED STATES PATENTS

